This study investigates the interaction between life-changes stress and personality dispositions as a predictor of health and illness. Relevant background includes a research theme showing that life changes stress is moderately related to illness. But, in study after study, a small group of hardy persons emerges symptom free even under conditions of great stress. Another relevant research theme shows that certain personality dispositions increase the likelihood of illness, whereas others are associated with vigorous health. In this work, the relationship between personality and illness is again only moderate. The moderate relationships provoke the present plan to pursue a fuller explanation of health and illness by studying the interaction between stress and personality. In this predictive study, a large group of lower, middle, and upper level management personnel will take questionnaires providing measures of degree of life changes stress, and of various personality dispositions. Then, at regular intervals over the following two years, they will also complete questionnaires concerning the presence and frequency of mental and physical symptoms. Multivariate analysis of variance and discriminant function analysis will be used to test the predictive importance of the interaction between stress and personality on symptomatology. As to significance, this research will show how certain personality dispositions can increase vulnerability to stress, whereas others can aid in tolerating or even thriving on stress. Having identified personality dispositions that make persons hardy, it will be possible in the future to educate others so that they can orient toward stress constructively rather than have to avoid it. This study can make a very real preventative contribution.